Question 3 - JN0-351 discussion

BFD is a protocol that can be used to quickly detect failures in the forwarding path between two adjacent routers or switches. BFD can be integrated with various routing protocols and link aggregation protocols to provide faster convergence and fault recovery.

According to the Juniper Networks documentation, the following protocols support BFD on Junos OS devices1:

BGP: BFD can be used to monitor the connectivity between BGP peers and trigger a session reset if a failure is detected.BFD can be configured for both internal and external BGP sessions, as well as for IPv4 and IPv6 address families2.

OSPF: BFD can be used to monitor the connectivity between OSPF neighbors and trigger a state change if a failure is detected.BFD can be configured for both OSPFv2 and OSPFv3 protocols, as well as for point-to-point and broadcast network types3.

LACP: BFD can be used to monitor the connectivity between LACP members and trigger a link state change if a failure is detected.BFD can be configured for both active and passive LACP modes, as well as for static and dynamic LAGs4.

Other protocols that support BFD on Junos OS devices are:

IS-IS: BFD can be used to monitor the connectivity between IS-IS neighbors and trigger a state change if a failure is detected. BFD can be configured for both level 1 and level 2 IS-IS adjacencies, as well as for point-to-point and broadcast network types.

RIP: BFD can be used to monitor the connectivity between RIP neighbors and trigger a route update if a failure is detected. BFD can be configured for both RIP version 1 and version 2 protocols, as well as for IPv4 and IPv6 address families.

VRRP: BFD can be used to monitor the connectivity between VRRP routers and trigger a priority change if a failure is detected. BFD can be configured for both VRRP version 2 and version 3 protocols, as well as for IPv4 and IPv6 address families.

The protocols that do not support BFD on Junos OS devices are:

RSTP: RSTP is a spanning tree protocol that provides loop prevention and rapid convergence in layer 2 networks. RSTP does not use BFD to detect link failures, but relies on its own hello mechanism that sends BPDU packets every 2 seconds by default.

FTP: FTP is an application layer protocol that is used to transfer files between hosts over a TCP connection. FTP does not use BFD to detect connection failures, but relies on TCP's own retransmission and timeout mechanisms.

1: [Configuring Bidirectional Forwarding Detection]2: [Configuring Bidirectional Forwarding Detection for BGP]3: [Configuring Bidirectional Forwarding Detection for OSPF]4: [Configuring Bidirectional Forwarding Detection for Link Aggregation Control Protocol] : [Configuring Bidirectional Forwarding Detection for IS-IS] : [Configuring Bidirectional Forwarding Detection for RIP] : [Configuring Bidirectional Forwarding Detection for VRRP] : [Understanding Rapid Spanning Tree Protocol] : [Understanding FTP]